Exemplo n.º 1
0
func (s *state) DecryptPacket(pkt *lob.Packet) (*lob.Packet, error) {
	s.mtx.RLock()
	defer s.mtx.RUnlock()

	if !s.CanDecryptPacket() {
		return nil, cipherset.ErrInvalidState
	}
	if pkt == nil {
		return nil, nil
	}

	if !pkt.Header().IsZero() || pkt.BodyLen() < 16+4+4 {
		return nil, cipherset.ErrInvalidPacket
	}

	var (
		nonce    [16]byte
		bodyRaw  []byte
		innerRaw []byte
		innerLen = pkt.BodyLen() - (16 + 4 + 4)
		body     = bufpool.New()
		inner    = bufpool.New().SetLen(innerLen)
	)

	pkt.Body(body.SetLen(pkt.BodyLen()).RawBytes()[:0])
	bodyRaw = body.RawBytes()
	innerRaw = inner.RawBytes()

	// compare token
	if !bytes.Equal(bodyRaw[:16], (*s.localToken)[:]) {
		inner.Free()
		body.Free()
		return nil, cipherset.ErrInvalidPacket
	}

	// copy nonce
	copy(nonce[:], bodyRaw[16:16+4])

	{ // verify hmac
		mac := bodyRaw[16+4+innerLen:]

		macKey := append(s.lineDecryptionKey, nonce[:4]...)

		h := hmac.New(sha256.New, macKey)
		h.Write(bodyRaw[16+4 : 16+4+innerLen])
		if subtle.ConstantTimeCompare(mac, fold(h.Sum(nil), 4)) != 1 {
			inner.Free()
			body.Free()
			return nil, cipherset.ErrInvalidPacket
		}
	}

	{ // decrypt inner
		aesBlock, err := aes.NewCipher(s.lineDecryptionKey)
		if err != nil {
			inner.Free()
			body.Free()
			return nil, err
		}

		aes := Cipher.NewCTR(aesBlock, nonce[:])
		if aes == nil {
			inner.Free()
			body.Free()
			return nil, cipherset.ErrInvalidPacket
		}

		aes.XORKeyStream(innerRaw, bodyRaw[16+4:16+4+innerLen])
	}

	innerPkt, err := lob.Decode(inner)
	if err != nil {
		inner.Free()
		body.Free()
		return nil, err
	}

	inner.Free()
	body.Free()

	return innerPkt, nil
}
Exemplo n.º 2
0
func (s *state) DecryptPacket(pkt *lob.Packet) (*lob.Packet, error) {
	s.mtx.RLock()
	defer s.mtx.RUnlock()

	if !s.CanDecryptPacket() {
		return nil, cipherset.ErrInvalidState
	}
	if pkt == nil {
		return nil, nil
	}

	if !pkt.Header().IsZero() || pkt.BodyLen() < lenToken+lenNonce {
		return nil, cipherset.ErrInvalidPacket
	}

	var (
		nonce    [lenNonce]byte
		bodyRaw  []byte
		innerRaw []byte
		innerPkt *lob.Packet
		body     = bufpool.New()
		inner    = bufpool.New()
		ok       bool
	)

	pkt.Body(body.SetLen(pkt.BodyLen()).RawBytes()[:0])
	bodyRaw = body.RawBytes()
	innerRaw = inner.RawBytes()

	// compare token
	if !bytes.Equal(bodyRaw[:lenToken], (*s.localToken)[:]) {
		inner.Free()
		body.Free()
		return nil, cipherset.ErrInvalidPacket
	}

	// copy nonce
	copy(nonce[:], bodyRaw[lenToken:lenToken+lenNonce])

	// decrypt inner packet
	innerRaw, ok = box.OpenAfterPrecomputation(
		innerRaw[:0], bodyRaw[lenToken+lenNonce:], &nonce, s.lineDecryptionKey)
	if !ok {
		inner.Free()
		body.Free()
		return nil, cipherset.ErrInvalidPacket
	}
	inner.SetLen(len(innerRaw))

	innerPkt, err := lob.Decode(inner)
	if err != nil {
		inner.Free()
		body.Free()
		return nil, err
	}

	inner.Free()
	body.Free()

	return innerPkt, nil
}